I have done some searching and reading about this very same problem but still dont know whats going on. I have a 96 powerstroke and it started to get the bad idle and loss of power. I unpluged the each harness on the valve covers. When i did the ones on the passengers side the truck almost died out but then idled back up to a rough idle. When ever i do either one on the drivers side there is no change. I went ahead and replace the UVCH and glow plugs and it still does it. If i unplug the ICP there is not change in the idle. There is no check engine light coming on either. Anybody have any ideas.